Lots of prepends - AS20912 case

Dorn Hetzel dhetzel at gmail.com
Fri Feb 20 13:51:26 UTC 2009

Replacing what is conventially thought to be a string with an integer
multiplier seems a massive violation of the principle of least astonishment.

On Fri, Feb 20, 2009 at 8:00 AM, Jon Lewis <jlewis at lewis.org> wrote:

> On Fri, 20 Feb 2009, Giuliano Peritore wrote:
>        The problem is that differently to Cisco the syntax of the prepend
>> field on thius system is not a string (eg. "20912 20912 20912") but an
>> integer, that the user interface _should_ limit to the interval 0-16.
> ...
>>       The producer has been warned about the problem, which I can't
>> completely define as a "bug"... but the lack of a user configuration helper
>> (syntax checker).
> More important than whether or not to consider this a bug, it seems a very
> shortsighted way to support prepending.  If your prepend "field" is an
> integer controlling how many times to prepend, how do you control which
> ASN(s) or even AS Paths are prepended?  It sounds like you probably can't.
> As has been discussed recently, there are cases where you might want to
> prepend a creative AS Path for traffic engineering purposes to force certain
> routes/paths to be ignored by certain ASNs.
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